That's a great idea, but I don't know of any built-in setting for that. Or in other words, you would need to do it by hand. You may have noticed that some extensions can be disabled at any time, while other extensions require a Firefox restart in order to disable them. For those with the newer "restartless" design, the developer can make them applicable to both regular and private windows, or only one or the other. I don't know whether Firefox can externally override those choices (either itself or using another extension). You might ask about this on the Add-ons site: https://discourse.mozilla-community.org/c/add-ons For the time being, you could use the Add-ons page, Extensions panel, but these changes would apply to all windows. Either: * Ctrl+Shift+a * "3-bar" menu button (or Tools menu) > Add-ons In the left column, click Extensions. Then you can Disable/Enable on the right side.